Glass strand is typically formed by attenuating filaments through orifices or tips at the bottom of a heated bushing containing molten glass. The filaments may be cooled by spraying them with water as they leave the bushing. The filaments are then passed across the application surface of an applicator where they are coated with a binder and/or size. The coated filaments are then gathered into strand form in a gathering shoe, which is typically a grooved cylinder or wheel formed of a material such as graphite. The strand may then be traversed across the face of a rotating spiral and wound as a forming package on a rotating collet carried by a winder. In another operation, the strand from the gathering shoe may be passed between cutting blades and chopped into particulate glass fiber strands. In a further alternative, the strand may be pulled between belts, wheels and the like of an attenuator and packaged in a container.
In any of the above operations, a significant amount of waste glass fiber strand is produced. In most of the above described operations, inconsistent diameter filaments result during start-up and slow down of the systems due to the fact that the filament diameter is inversely proportional to the speed of attenuation for a given bushing.
Further, such occurrences as low speed attenuation during doffing of the forming package, restarting the strand formation after a strand breakout, and the like are all examples of instances where the formation of waste strand occurs.
In the past, waste filaments were passed through the forming operation in the same manner as production quality filaments until they had passed the gathering shoe and were formed into strand. Only at this point were they segregated as waste. All of the waste strands and the filaments forming them were coated with the binder and/or size, in the same manner as the production quality material. Since binder and/or size which is coated onto filaments cannot be recovered, and since waste strand may represent up to about 15 percent of the production of a typical glass fiber forming position or more, it is obvious that the prior art strand formation methods consume a significant amount of binder and/or size which is in actuality being discarded as waste. It is, therefore, desirable to eliminate or substantially reduce the amount of binder and/or size which is wasted by being coated onto waste filaments.
A second problem encountered with the continual coating of filaments with binder and/or size occurs from the necessity of the forming level operator to manually handle the strands during such operations as start-up, and other occurrences of a glass fiber forming operation. To begin the winding of a new forming package on a collet, to begin the chopping of strand, to thread an attenuator, and to restart any of these attenuation devices after a breakout of strand occurs, the operator normally feeds strand to the operation manually. This requires physical contact between the operator's skin and the coated strand. Some binders and/or sizes may have adverse dermatological effects on an operator's skin from the constant physical contact of the operator's hands with coated strands. It is also desirable, therefore, to reduce substantially or eliminate physical contact between the operator and glass strand having irritating binders and/or sizes coated thereon.
A method for reducing both binder and/or size consumption and physical contact with binder and/or size coated strand is disclosed in concurrently filed application Ser. No. 775,483 of David M. Griffiths, which is incorporated herein by reference. The present invention provides apparatus to carry out the method of the copending application.